Well there is a bunch of standards aimed at this, already mentioned are EDI and cXML. But another very ambitious is Oasis' UBL. In Denmark and a few other european countries you basically have to support invoicing in UBL (Or more specifically the danish subset OIOUBL or scandinavian subset NESUBL) if you want to do business with government as it is a requirement.[1] In a transition-phase (which i don't know if still is ongoing) suppliers could send invoices to a "scanning agency" that would attempt to convert the invoice to OIOUBL and send on to the government institution.
This has pushed adoption of these things in Denmark quite a bit and we see a lot of big corporations demanding of their suppliers that they support these formats.
I use this daily in VS2010, and have used ViEmu in previous VS versions.
Generally, I like it, but it can be a bit sluggish at times. The only plugin I have running is JSLint, so I suspect it's VSVim causing the problems (though it only generally bogs down when I leave VS2010 for a bit). The keybindings work as one would expect. As I mentioned in a different thread, I wish it could break out of the tabbed window convention of VS and use buffers.
ViEmu did feel a bit faster (and was less prone to crashing).
What version are you using? Prior to 1.2 there was a nasty perf bug with :hlsearch that caused it to be sluggish with 1) very large files or 2) a good number of files opened. The bug is mostly fixed in 1.2 but there are still a couple of corner cases. Those are addressed in 1.3 which will be released sometime next week. A beta drop is available here
I can chime in as I just purchased ViEmu. It's really wonderful to have all the Vim bindings present in studio (and the rest of Office!). I haven't noticed any speed issues and I haven't noticed bugs (yet), but I've only been using now daily for two weeks and I haven't installed any plugins for it.
This has pushed adoption of these things in Denmark quite a bit and we see a lot of big corporations demanding of their suppliers that they support these formats.
Edit: [1] Previous to OIOUBL danish government had its own format called OIOXML: http://en.wikipedia.org/wiki/OIOXML